Air heater



Feb. ll, 1930.

H. A. ATWATER AIR HEATER Filed Nov. 14, 1927 5 Sheets-Sheet l A TTORNE YFeb; 11, 1930. H. A` ATwATER 1.746,982

AIR HEATER Filed Nov. 14, 1927 5 Sheets-Sheet 2 A TTORNE Y Feb. 11,1930. H. A. ATWATER 1,746,982

AIR HEATER Filed Nov. 14. 1927 5 Sheets-Sheet 3 IN VEN TOR Harig] fl.Hiv/diei, Inra/WMM ATTORNEY Patented Feb. 11, 1930 PATENT; OFFICE HARRYA. ATWATER, OF KANSAS CITY, MISSOURI AIR HEATER Application led November14, 1927. Serial No. 233,082.

The present invention relates to heat eX- change apparatus, and aims toprovide a novel, improved and more efficient apparatus for airpreheating purposes through the medium of heat recovered from the wasteflue gases, in connection with furnace and boiler equipment.

One of the objects of my invention is to provide an apparatus in whichthe heat eX- change is carried on in a more effective and economicalmanner, by reversing the usual method of conducting the air and heatingmedium through the apparatus, whereby I cause the flow of air to bepreheated to take place through the space between the gas tubes or fiuesand the interior wall surfaces of the housing or casing, while the hotgases are conducted in the opposite direction through said tubes orflues. i

A further object of the invention isto provide a construction in whichthe tendency of the parts to become warped or distorted 1s reduced to aminimum by providing` connections which permit the necessary compensat 5ing movement in response to temperature changes at those points wheremore or less destructive strains would otherwise be imposed upon theconnections or joints on account of such changes in temperature. In

carrying out this purpose, I provide connections between the hot gastubes or iues and the adjacent structural work which will permit of alimited amount of relative play or slidingaction, while preventing anyleakage 5 of air or gas to any such extent as would materially diminishthe efficiency of the operation.

A further object of my invention is to provide hot gas tubes or flues ofa type which will permit either reversal of position thereof, orconvenient replacement of the units from time to time, as required.

lVith the foregoing general objects in View,

the invention will now be described by reference to the accompanyingdrawings, illustratino' one form of apparatus or equipment which I havedevised for embodying the proposed features of improvement, after whichsuch features and combinations thereof deemed to be novel will be forthand claimed.

In the drawings Figures 1 and 2 are fragmentary elevations illustratinga portion of the air intake side and also a portion of the air outletside, respectively, of my apparatus;

Figure 3 is a vertical sectional elevation of the apparatus,representing a section taken on the line III-III of Figure l;

Figure 4 is a perspective view illustrating in detail a portion of theinterior structure of the apparatus, comprising the tubes or tlues andspacing members;

Figure 5 is a fragmentary longitudinal sectional elevation, representinga section 'taken partly along the line V-V of Figure 7;

Figure 6 is an enlarged detail perspective showing a portion of one ofthe collar members for the upper ends of the gas flues or tubes;

Figure 7 is an enlarged vertical sectional detail View, taken on theline VII-VII of Figure 10 and illustrating the connections between thehousing and casing and the upper 7 collar members;

Figure 8 is a horizontal section on the line VIII-VIII of Figure 7Figure 9 is a plaif View, partly broken away, showing one of the tubespacing plates; and

Figure l0 is a broken plan view, showing a portion of the top of theapparatus.

In the usual construction of air preheating devices or recuperators, asnow commonly followed, it has been the practice to conduct the air to bepreheated through the several units of the flue or tube assembly,leaving' the hot gas to pass through the space between the tubes orflues and the outside casing of the 90 apparatus. In such practice,since the eX- pansion of the tubes or flues is not materially greaterthan that of the casing or outside housing, it is practicable to securethe tube structure rigidly and permanently in place, without providingfor any compensating movement between the tube assembly and the outsideframework. In all such ap paratus, however, there is present a certainamount of expansion and contraction, with particularly set the usualstrains imposed upon the struetural elements, which can only beabsorbed, where there is no compensating movement provided for, by awarping, twist-ing, or other deformation of these parts of thestructure.

In this connection it seems that prior practice has laid undue emphasisupon the question of leakage or non-leakage ofthe parts of thesepreheater constructions, due to an apparently mistaken notion that thestructure must be maintained practically air or gas-tight; and yet evenin those constructions where permanently secured and immovableconnections were provided between the tube or iiue. assembly and theoutside framework, whereby an originally air-tight structure wassecured, it seems quite certain that the apparatus could not possiblyremain indefinitely in this air and gas-tight state, due to thenecessity of the contraction and expansion strains being absorbed by thewarping and distortion of the tube assembly and its connections to theoutside framework.

However, wien it is remembered that the {iow of air conducted throughthe apparatus is at a relatively low pressure, and the negative pressureor suction of the hot gas How is a similarly weak factor, it will atonce be seen that no leakage of any material consequence can take placethrough any small cracks or crevices wiich may be present in the tubestructure or its connections, if the area of such openings is kept downto as small an extent as possible, rllherefore, if joints of a slidingcharacter, or connections of any other compensating nature, be providedbetween the tube assembly and the remaining structure of the apparatus,and the areas of the crevices between the relatively moving elements ofthese connections be maintained as small as possible in lcomparison withthe areas of the main air and gas passages there will be a negligibleleakage by way of these compensating connections, since itis of courseobvious that the air and gas flow will follow the least restrictedcourse.

As has already been stated, the practice heretofore has been to conductthe air to be preheated through the ducts, or tube or flue assembly, andsimultaneously to cause the hot flue gases to flow through the spacebetween this assembly and the interior face of the casing or housing.Thus the housing or casing as well as the metal of the tubes or ducts issubjected to the extreme heat of the lue gases, so that the heat effectupon the casing is practically the same as that taking place in thetubes. In the practice proposed by my invention, a reversal of thismethod is adopted, in that l conduct the hot flue gases through theducts or tubes of the flue assembly, and simultaneously cause the air tobe preheated to 'liow through the space between this tube or flueassembly and the interior walls of the casing. By this method it isapparent that the stages of the temperature are stepped up moregradually from the exterior of the housing to the interior of the chiotsor tubes, and the metal of the casing is not subjected to such extremesin temperature. As a result, the expansion changes in the duct-s 0rtubes are materially greater than those taking place in the casing,compared with former practice; and in addition to effecting increasedeconomy, due to less loss of heat to the outside atinosphere, 1 am ableto confine the more important variations by contraction and expansion,due to temperature changes, to the tube assembly and its connections,where the compensating features of my invention are introduced.

Referring now to the drawings in detail, these illustrate my inventionas embodied in an apparatus comprising an exterior housing or casingmade up of sheeting 12 supported and braced by angles 111, the top andbottom of the housing being open for the passage therethrough of the hotflue gases, while a flanged air intake opening 16 is provided throughone side of the housing near the top (Figures 1 and 3), and a similarair discharge opening 18 is provided through the opposite side of thehousing near the bottom (Figure 2). Jfipertiue-d plates 19 are securedto the upper corners of the housing for convenience in lifting orotherwise handling the apparatus. Opposite to the opening 18 is alsoprovided an opening 2O for assembly and clean-out purposes, and normallyclosed by a sheet of asbestos 21 and plate 22, as illustrated in Figure3.

Each of the gas chiots comprises a tube member of sheet metal. shaped toprovide a relatively thin iiue element 24, open at top and bottom topermit the movement of the gases upward through the tube assembly. Thetubes are of a width substantially equal to that of the interior of thecasing 12, and their side margins 2al are tapered so as to widen the airspace between the tubes at these points as indicated at 25 in Figures 4and 8, and thereby forming flaring intake and outlet passages to producestream-line effects at the openings 1G and 18, respectively.

The base framework of the apparatus includes longitudinal channels 26,to which are secured in gas-tight relation, as by welding, the ends oftransversely extending collar members 2S which are of a size and shapeadapted for slidingly engaging (with a snug lit) the lower ends of thetubes 2e as shown in Figure 5. Each pair of adjoining collars 28 isconnected by a tapered closure portion 29 for closing up the lower endsof the air spaces between the tubes, and also forming the tapered gasinlet openings to the gas passages between the tubes, as shown inFigures 4 and 5. For further sealing effect, spacing bars 35 comprisedof sheet metal packed with asbestos 36, are mounted transversely betweenthe collars 28 and over the closure portions 29, these bars serving alsoto space and brace the collars and the telescoping lower ends of thetubes 24.

Inside each closure member are secured, as by welding, the lower ends ofa. series of angles 30, in spaced, parallel and upwardly projectingrelation, for extending the whole length of the tubes 24, and therebybracing and stiflening the same and preventing any collapsing tendencyas well as splitting up or laning the iiow of hot gases through thetubes. At their upper ends the angles 30 are secured to a strap or bar82, whereby they are held apart in equally spaced relation.

rlhe tubes 24 are further strengthened and stitlened by means oflaterally projecting fins or ribbons 34 secured by welding to one faceof each tube in equally spaced and parallel relation for cooperatingwith the next adjoining tube in laning the tlow of air through thespaces between the tubes.

At the top of the apparatus is arranged a series of separate andindependently removable collar members, in general similar in size andshape, when assembled, to those already described. ln Figure 6 isillustrated a perspective view of an end portion of one of said collarunits, the same comprising a closure portion 29 connecting two sidecollar forming portions 28 and terminating in the flaring end 28H forfitting Within the tapered side margins 24 of the tubes. As illustratedin Figure 5, in assembling, each pair of adjoining collar unitscooperates to provide the collar structure for telescoping within theupper end of one of the tubes, and an upper set of spacing bars 35 isused for spacing and bracing the parts at the upper ends of the tubes,the same as at the lower ends.

Along each side of the framework of the casing or housing, near the topthereof, I also secure to a fixed channel member 39, as bywelding, anotched spacing plate 37, with the notches or recesses 38 of said platefacing inward for embracing the converging margins 24 of the tubes,thereby holding the same apart in the proper spaced relation.

At each end of each of the upper collar members is secured an angleelement 40 servine to close the ends of the closure portion 29, and alsoprojecting into position for engagement between a pair of asbestospacking strips 41, as shown in Figure 7. Each of the upper strips 4l isengaged by a follower bar or plate 42 engaged by adjustable clampingscrews 43, threaded through an angle piece 44 removably attached bybolts 45 to the upper framework. Each of the lower packing strips 41rests upon the fixed channel member 39, and with the parts assembled asillustrated in Figure 7 it is apparent that the same are securely heldtogether in substantially gas-tight relation, and at the same time byremoval of the angles 44 and bars or lates 42, access may be had to thetube assem- Ely for removal or replacement of such tube elements as mayrequire attention from time to time.

It is thus apparent that l have devised a practical and etlicientapparatus for carrying out thevarious desired objects ofthe invention,as above set forth. By conducting the hot gases through the tubes 24instead of through the space between the tube assembly and the casing, amore gradual stepping up of the temperatures from that of the outsideatmosphere to the interior of the tubes is obtained, with the resultthat the casing is not subjected to Such extreme temperature variations,and the loss of heat through the casing by radiation is reduced; at thesame time there is less oxidation and scaling ed of the casing metal.The sliding and telescopic character of the joints between the tubes andcollar members permits all relative movement necessary to compensate forthe temperature changes in the tube assembly, and, forreasons alreadygiven, the leakage past these telescopic joints is altogethernegligible, and is more than offset by the advantages gained by thecompensating character of the tubes and their connections. The removabletube structure, whereby these may be reversed or replaced, is also avery desirable and practical feature in prolonging the useful life ofthe apparatus.

While l have herein described and illustrated what l have found vtoconstitute a very practical and satisfactory form of embodiment of theinvention, l desire to reserve the right to make all such changes ormodilica.- tions as may fairly fall within the scope of the appendedclaims.y y

Having thus described my invention,l what I claim and desire to secureby Letters Patent is l. An air preheating apparatus comprising a housingor casing provided with oppositely located air receiving and dischargeopenings, a series of liXed collar members at the lower ends of saidhousing, a series of collar members providing removable collarconnectionsV at the upper end of said housing, and a plurality ofindependent conduit elements each open at both ends and slidinglyconnected with said collar-members at both the upper and lower ends ofthe housing.

2. An air preheating apparatus comprising a housing or casing providedwith oppositely located air receiving and discharge openings, a seriesof collar members secured in fixed and spaced relation at the lower endof said housing, a series of collar members providing spaced andremovable collar connections at the upper end of the housing, aplurality of conduit element-s each open at both ends and slidinglyconnected with said collar members at both ends of said housing, andmeans for closing the spaces between adjoining conduit elements at bothends thereof.

3. An air preheating apparatus comprising a housing or casing providedwith oppositely located air receiving and discharge openings, a seriesof collar members secured in fixed and spaced relation at the lower endof said housing, a series of collar members providing spaced andremovable collar connections at the upper end of the housing, aplurality of conduit elements each open at both ends and slidinglyconnected with said collar members at both ends of said housing, meansfor closing the spaces between adjoining conduit elements at both endsthereof, and combination packing and spacing bars removably mountedbetween the upper and lower ends of said conduit elements for spacingthe same and for sealing the spaces between the ends thereof.

4. An air preheating` apparatus compris ing a housing or casing providedwith oppositely loca-ted air receiving and discharge openings, a seriesof xed collar members at the lower ends of said housing, a series ofcollar members providing removable collar connect-ions at the upper endof said housing, a plurality of independent conduit elements each openat both ends and slidingly connected with said colla-r members at boththe upper and lower ends of the housing, and means carried by said lowerseries of collar members for forming interior bracing for said conduitelements and dividing the gas flow therethrough.

5. An air preheating apparatus comprising a. housing or casing providedwith oppositely located air receiving and discharge openings, a seriesof fixed collar members at the lower ends of said housing, a series ofcollar members providing removable collar connections at the upper endof said housing, a plurality of independent conduit elements each openat both ends and slidingly connected with said collar members at boththe upper and lower ends of the housing, and fixed spacing devicesremovably engaging the upper ends of said tubes for maintaining the samein rigidly spaced relation.

6. An air preheating apparatus comprising a housing or casing providedwith oppositely located air receiving and discharge openings, a seriesof fixed collar members at the lower ends of said housing, a series ofcollar members providing removable collar connections at the upper endof said housing, a plurality of independent conduit elements each openat both ends and slidingly connected with said collar members atbot-hthe upper and lower ends of the housing, and means for removablyretaining said upper series of collar members in communicating relationwith the upper ends of said conduit elements.

In witness whereof I hereunto aix my signature.

HARRY A. ATVATER.

